How to update json field using jq [duplicate] - json

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Transfer or merge only some properties from one JSON file to another with jq
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jq to replace text directly on file (like sed -i)
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Closed 8 days ago.
I have a bootstrap script. After every time it runs, I want to keep track of its exit status in a JSON file. JSON file can have other fields too.
Case 1: The very first time it runs, JSON file will be created & a field node_bootstrap_status with boolean value will be added to it.
Case 2: In subsequent runs, JSON file will pre-exist. But in this case, I want to update same JSON field node_bootstrap_status with the outcome(again boolean).
I wrote the following bash script. It works for 1st case. In second case however, it ends up deleting everything in pre-existing JSON file.
exit_code=1
node_info_file="/etc/node_info.json"
if [[ -f $node_info_file ]]; then
# /etc/node_info.json exists
echo "${node_info_file} exists"
if [ $exit_code = 0 ]; then
cat $node_info_file | jq --argjson node_bootstrap_status true '{"node_bootstrap_status": $node_bootstrap_status}' > $node_info_file
else
cat $node_info_file | jq --argjson node_bootstrap_status false '{"node_bootstrap_status": $node_bootstrap_status}' > $node_info_file
fi
else
# /etc/node_info.json does NOT exists
echo "${node_info_file} does not exist"
touch ${node_info_file}
if [ $exit_code = 0 ]; then
echo '{}' | jq --argjson node_bootstrap_status true '{"node_bootstrap_status": $node_bootstrap_status}' > $node_info_file
else
echo '{}' | jq --argjson node_bootstrap_status false '{"node_bootstrap_status": $node_bootstrap_status}' > $node_info_file
fi
fi
expected outcome:
cat /etc/node_info.json
{
"node_bootstrap_status": true/false,
"foo": "bar"
}

Answer 1

You're off to a good start - but you'd want to use assignment rather than the sort of { ... } syntax like so:
node_info_file="node_info.json"
set_status() {
local value="$1"
mv -f "$node_info_file" "$node_info_file.tmp"
# Set property key with: '.node_bootstrap_status = ...'
jq --argjson node_bootstrap_status "$value" '.node_bootstrap_status = $node_bootstrap_status' "$node_info_file.tmp" > "$node_info_file"
rm -f "$node_info_file.tmp"
}
# if node_info.json does NOT exists; create it
if [ ! -f $node_info_file ]; then
printf '%s\n' '{}' > "$node_info_file"
fi
set_status true
set_status false
I tested this with empty JSON, and with other contents, and it worked as expected.
Also, make sure you quote "$node_info_file" - it's good practice. If you use ShellCheck then it'll catch those types of errors for you.

Answer 2

Try to adapt this version to your needs :
#!/usr/bin/env bash
exit_code=1
node_info_file="/etc/node_info.json"
test -f "$node_info_file" || echo {} > "$node_info_file"
[ $exit_code = 0 ] && status=true || status=false
tmp=$(mktemp)
jq --argjson node_bootstrap_status $status '{$node_bootstrap_status}' "$node_info_file" > $tmp
mv $tmp "$node_info_file"
Just a side note, it may not be a good idea to save node_info.json in /etc.